[Media Router] Custom Controls 1 - Add MediaStatus, MediaRouteController, and mojo interfaces

chrome/browser/media/router/media_route_status_observer.h

+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CHROME_BROWSER_MEDIA_ROUTER_MEDIA_ROUTE_STATUS_OBSERVER_H_
+#define CHROME_BROWSER_MEDIA_ROUTER_MEDIA_ROUTE_STATUS_OBSERVER_H_
+
+struct MediaStatus;
+
+namespace media_router {
+
+// An interface for observing updates to the status of a Media Route.

[mark a. foltz, 2017/03/06 20:06:19]

How is this interface specific to Media Routes?   Can it just be
MediaStatusObserver?

[takumif, 2017/03/08 04:24:02]

No, it's not really specific to media routes, but I didn't want to name it
MediaStatusObserver because it doesn't implement
media_router::mojom::MediaStatusObserver. Also, when I named this class
MediaStatusObserver I had the compiler interpret it as the mojo variation in
some instances that led to weird errors, so I thought it'd be better to make it
less ambiguous. The same for MediaRouteController vs mojom::MediaController.

[mark a. foltz, 2017/03/08 22:16:12]

Only generated mojo bindings should be in the mojo:: namespace; and I believe
even type-mapped types will be referenced with the proper namespace.  Maybe you
can show me the errors you're seeing?

[takumif, 2017/03/09 19:45:30]

There was a case where I was in the media_router namespace and the compiler
confused "MediaStatusObserver" with "media_router::mojom::MediaStatusObserver"
even though I wasn't in the mojom namespace. Perhaps it was because I was within
a class whose superclass was in the mojom namespace? I just thought that this
could cause more confusion in the future.

[mark a. foltz, 2017/03/13 18:22:30]

Maybe you don't need this class at all?  Since you are type mapping, it looks
like it will be identical to mojom::MediaStatusObserver.

+class MediaRouteStatusObserver {
+ public:
+  MediaRouteStatusObserver() {}

[imcheng, 2017/03/06 23:11:41]

Constructors aren't required for interfaces. Also similar comment to mfoltz@'s,
it doesn't seem specific to a MediaRoute.

[takumif, 2017/03/08 04:24:02]

Removing the ctor, but I'm a bit hesitant to name this MediaStatusObserver.

+  virtual ~MediaRouteStatusObserver() {}
+
+  virtual void OnMediaRouteStatusUpdated(const MediaStatus& status) = 0;
+};
+
+}  // namespace media_router
+
+#endif  // CHROME_BROWSER_MEDIA_ROUTER_MEDIA_ROUTE_STATUS_OBSERVER_H_